Ubiquitous computing refers to building a global computing environment where seamless and invisible access to computing resources is provided to user anytime anywhere. A ubiquitous computing environment can be implemented on the basis of well-internetworked computing devices for recognizing situations of everyday human life space.
In order to recognize the situations, the ubiquitous computing system collects data transmitted by sensors around target regions. Typically, cluster-based sensor network provides an efficient architecture for collecting the data detected by the sensors. The sensor network is composed of a large number of sensor nodes having capabilities to collect data in response to a request sent by a sink node and route collected data back to the sink node.
In the conventional cluster-based wireless sensor network, however, frequent data request by the sink node and data reporting by the sensor nodes increase traffic and processing loads of the sensor network, resulting in reduction of network life time.